1. Field of the Invention
This invention relates to focus adjusting devices and more particularly to a device for axially moving a lens barrel.
2. Description of the Prior Art
It is known to provide a lens barrel moving device in the form of a helicoid thread on the lens barrel. The arrangement of the helicoid thread groove in the lens barrel is, however, very difficult from the point of view of machining and the formation of the helicoid thread directly in the lens barrel gives rise to a problem in that when the lens barrel is axially moved, it is caused to rotate about the optical axis thereof simultaneously. For this reason, the conventional device for axially moving the lens barrel by the use of the helicoid thread necessitates a supplementary mechanism for constraining the lens barrel from rotative movement. This calls for a large increase in the complexity of the structure of the control device for the lens barrel and the bulk and size thereof.